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Browsing by Author "Neumann, Michael L."

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    Mapping Nonsquare and Unevenly Spaced 2-D SLDV Data of an Aircraft Fuselage by Using Spatial DFT-IDFT Techniques
    Li, William Xinzuo; Mitchell, Larry D.; Lu, Min-Fu; Neumann, Michael L. (Hindawi, 1996-01-01)
    The scanning laser Doppler vibrometry (SLDV) technique provides velocities of a structure at 2-dimensional (2-D) angularly evenly spaced (in the laser scanning sense) data points. This causes an unevenly spaced data point distribution on the surface of the test structure. In many cases evenly spaced data point distribution with square or rectangular grids is highly desirable. In this study the SLDV velocity data of a partial surface area of an aircraft fuselage were mapped to truly spatial evenly spaced coordinates by using the spatial DFT-IDFT technique with minimum distortion. This 2-D data mapping technique certainly is not limited to the fuselage, hut can he very useful for many other 3-D structures.
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    A method for the spatial functionalization of the dynamic response of a structure with structural stability considerations
    Neumann, Michael L. (Virginia Tech, 1993)
    The scanning Laser Doppler Vibrometer (LDV) has developed into a useful tool for rapidly acquiring spatially dense structural dynamic response information in a noncontacting manner. The research presented in this paper is part of a larger project at the Structural Imaging and Modal Analysis Laboratory in the Department of Mechanical Engineering at Virginia Polytechnic Institute and State University, Blacksburg, VA, to develop a six-degree-of-freedom (6-DOF) structural response model based on experimental data. This paper represents a portion of the research for the 6-DOF structural imaging project. A method for creating a functionalized description of a discreetly sampled 2-D data field containing response measurements evenly spaced in laser scan angie coordinates is presented. A filtering process involving a median and edge-median filter algorithm followed by a Discrete Fourier Transform/low-pass spatial frequency domain filter/Inverse Discrete Fourier Transform algorithm is used to reduce the effect of errant data recorded by the LDV data acquisition system. A means of evaluating the performance of this process is developed. Finally, an experiment to determine the relationship between structural response stability and ambient temperature and relative humidity is presented. The response of a lightly damped structure was studied over a twenty-six hour period. A direct relationship between temperature and the dynamic response of the structure was found. This study is important to the overall 6-DOF project since structural stability is assumed in merging the various scans of the structure to obtain 6-DOF information. Recommendations are given for further research of topics discussed in this thesis.